Variations of dissolved greenhouse gases (CO2, CH4, N2O) in the Congo River network overwhelmingly driven by fluvial wetland connectivity

We report the spatial variations of dissolved carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations in the lowland part of the Congo River network obtained during ten field expeditions carried out between 2010 and 2015, in the eastern part of the basin (Democratic Republic of Congo). The integrated CO2 emission from the Congo River network is more than three times higher than the estimate of terrestrial net ecosystem exchange (NEE) on the whole catchment (77 TgC yr-1). This shows that it is unlikely that the CO2 emissions from the river network were sustained by the hydrological carbon export from terra firme soils (typically very small compared to terrestrial NEE), but most likely, to a large extent, they were sustained by wetlands (with a much higher hydrological connectivity with rivers and streams).